1. Field of the Invention
This invention relates to a hybrid suspension position and body velocity sensor as well as to an associated automotive suspension control system.
2. Description of Related Art
Automotive suspensions employing adjustable suspension units typically utilize one or more sensors for detecting the vertical position of a controlled road wheel and tire assembly with respect to either another part of the suspension itself or another part of the chassis or body of the vehicle. In the case of vehicles using load leveling or air or hydropneumatic suspension systems, it is necessary to know the ride height of the vehicle in order to determine whether correction of the ride height is required. If the suspension position sensor indicates that the ride height is less than a prescribed low limit, the adjustable suspension unit will be given the command to increase the ride height. Conversely, in the event that sensed ride height exceeds a prescribed high limit, the adjustable suspension unit will be given the command to lower, or decrease, the ride height.
Vehicular height sensors are useful not only with ride height adjusting systems but also as transducers for use with adjustable suspension dampers. It is known for example to control suspension dampers based upon data concerning the speed of the suspension movement in jounce or rebound.
Certain other suspension control algorithms utilize information concerning the vertical velocity of the vehicle's body. U.S. Pat. Nos. 3,807,678 and 4,696,489 disclose control systems in which accelerometers are employed for the purpose of sensing the vertical velocity of a vehicle body. A second sensor is employed with each of the systems of the '678 and '489 patents for determining the vertical velocity of the suspension and wheel and tire assembly with respect to the body of the vehicle. These two vertical velocities are compared and then as a result of such comparison a damping setting is chosen for an adjustable suspension unit. It should be noted that in each of the systems of the '678 and '489 patents a separate accelerometer is required to provide a signal which may be integrated to provide a signal representative of body vertical velocity. The body vertical velocity signal is then used, as previously described, in a control algorithm for operating the adjustable suspension units.
U.S. Pat. No. 4,625,993 illustrates another type of control system in which an accelerometer is used for the purpose of sensing body vertical velocity.
U.S. Pat. No. 4,065,154 describes a control system in which damping of an adjustable suspension unit is prescribed as a function of a pressure signal from the damper and the velocity of the wheel with respect to the body.
It is an object of the present invention to provide a hybrid suspension position and body velocity sensing system for an automotive suspension control system requiring only a single sensing element for not only suspension position but also body vertical velocity information. It is an advantage of the present invention that a sensing system according to this invention obviates the need for accelerometer for the purpose of generating signals representative of body vertical velocity.
It is an advantage of the present invention that a sensing system according to this invention may be used not only with adjustable suspension units capable of controlling vehicle ride height and suspension damping, but also with adjustable suspension units in which only suspension damping is variable.
Other objects, features and advantages of the present invention will become apparent to the reader of this document.